The present invention relates to devices for delivering, administering or dispensing substances, and to methods of making and using them. More particularly, the present invention relates to a fluid system comprising a flow system for the passage of a fluid wherein a flow in the flow system may be changed if an event occurs. For example, in one embodiment, the invention relates to a fluid system for a device for blood sugar determination in which a flow of a fluid is interrupted, stopped or diverted in the event of a malfunction of the blood sugar determination device.
Fluid systems in which fluids are conveyed through a flow system, having an inlet and an outlet for the liquid and one fluid line or a multiplicity of fluid lines leading from the inlet to the outlet, are used in a variety of technical fields. In medical technology in particular, a reliable function of such a fluid system is important because a malfunction of the fluid system poses a number of risks to the user or patient. For example, if a fluid active substance, for instance insulin, is being transported, a malfunction can lead to an inadequate dosage or an overdosage of the active substance. When a measurement solution is being transported, a malfunction can lead to imprecise or false measurements, or the patient may be put in danger because of an incompatibility of the measurement solution.
In order to ensure user safety, the fluid system can have a safety device which, by measuring a control parameter, for example the pressure in the fluid system, registers a malfunction of the fluid system and thereupon interrupts the flow of liquid in the flow system.
Such a safety device is desirable, for example, in a measurement method in which a measurement probe with a dialysis membrane is introduced into a patient's tissue and a measurement liquid is guided through the measurement probe. One example of a measurement method of this kind is the determination of blood sugar values of a patient suffering from diabetes. The measurement liquid may, for example, be introduced into the probe from an ampoule by way of a fluid system. In order to measure a blood sugar value, the measurement liquid is conveyed at a constant pressure through the flow system of the probe. The probe is introduced into the patient's body tissue in such a way that the measurement liquid comes into interaction with the environment of the tissue via the dialysis membrane. If, for example, a leak were to occur in the dialysis membrane inside the tissue, the measurement liquid would flow out of the flow system and into the tissue. A malfunction of this kind can be determined, for example, by the associated drop in pressure or complete loss of pressure in the flow system. In the event of such a malfunction, it is desirable, at least for the safety of the patient, to suppress the stream of measurement liquid in the flow system, so that no measurement liquid gets into the tissue.